Root Mean Square (RMS) voltage is easiest described as the equivalent constant voltage of a pulsed voltage output.
Not all e-cigs are created equal. Some have a smooth and flat voltage output...
(Blue line)
Some have a pulsed output...
For the smooth flat outputs, nothing special is needed. The voltage can be measured with any off the shelf cheap voltage meter.
For the pulsed output it gets a little more complicated. Most APV's that use a pulsed output are using a pulses of ~6 volts followed by ~0.0 volts. Traditionally, the setting on the screen or dial was programmed for the average voltage. If you have 6.0v for half of the time, and 0.0v for half of the time, then you have an average voltage of 3.0v (shown in the pulsed output image above). This was fine for a little while until vapers started talking about how certain APVs "hit harder" than others, saying that the APV was not accurate. Truth is that, where voltage is concerned, most of them are very accurate; you set the voltage, you get that voltage. The problem is that we dont vape a voltage. You can get the same experience from many different voltage levels by changing the resistance proportional to the voltage. This equates to watts.
A Watt is a measure of power. This power translates to heat, and heat+liquid translates to your taste. So what does this have to do with RMS?
Wattage is calculated as the square of the Voltage divided by the Resistance.
Root Mean Square is defined as: The square root of the mean (average) of the squares of the original values.
So using an example of 6.0v half the time and 0.0v half the time...
Square
6^2 = 36
0^2 = 0
Mean
(36+0)/2 = 18
Root
SQRT(18) = 4.242v
So our 3.0v setting has a 3.0v AVERAGE, but an equivalent constant voltage of 4.24vRMS.
But there is something missing....how do all of these voltage numbers relate to the vape? I said above that we dont vape a voltage, we vape watts, right?!?
First we'll make a few assumptions:
Same 6v/0V pulsed output, set at 3.0v with a 2.0 ohm cartomizer.
Lets figure the wattage for the pulses.
(Watts=V^2 / R)
6^2 / 2 = 18 watts for half the time
0^2 / 2 = 0 watts for half the time
Mean (Average) of 9 watts.
Then using Ohm's Law, we can input the average wattage and the resistance to calculate the RMS voltage; SQRT(P x R)
SQRT(9 x 2) = SQRT(18) = 4.242vRMS
If there is one thing to remember, it is that VRMS is not a replacement for VAVG. RMS is just a way to accurately state the equivalent constant voltage. The problem with VRMS is that you cannot easily and accurately calculate the amperage. With as much stress that is placed on battery safety, it is important to know what you are asking from your batteries.
Thanks for reading, feel free to leave questions or comments below.
Not all e-cigs are created equal. Some have a smooth and flat voltage output...
(Blue line)
Some have a pulsed output...
For the smooth flat outputs, nothing special is needed. The voltage can be measured with any off the shelf cheap voltage meter.
For the pulsed output it gets a little more complicated. Most APV's that use a pulsed output are using a pulses of ~6 volts followed by ~0.0 volts. Traditionally, the setting on the screen or dial was programmed for the average voltage. If you have 6.0v for half of the time, and 0.0v for half of the time, then you have an average voltage of 3.0v (shown in the pulsed output image above). This was fine for a little while until vapers started talking about how certain APVs "hit harder" than others, saying that the APV was not accurate. Truth is that, where voltage is concerned, most of them are very accurate; you set the voltage, you get that voltage. The problem is that we dont vape a voltage. You can get the same experience from many different voltage levels by changing the resistance proportional to the voltage. This equates to watts.
A Watt is a measure of power. This power translates to heat, and heat+liquid translates to your taste. So what does this have to do with RMS?
Wattage is calculated as the square of the Voltage divided by the Resistance.
Root Mean Square is defined as: The square root of the mean (average) of the squares of the original values.
So using an example of 6.0v half the time and 0.0v half the time...
Square
6^2 = 36
0^2 = 0
Mean
(36+0)/2 = 18
Root
SQRT(18) = 4.242v
So our 3.0v setting has a 3.0v AVERAGE, but an equivalent constant voltage of 4.24vRMS.
But there is something missing....how do all of these voltage numbers relate to the vape? I said above that we dont vape a voltage, we vape watts, right?!?
First we'll make a few assumptions:
Same 6v/0V pulsed output, set at 3.0v with a 2.0 ohm cartomizer.
Lets figure the wattage for the pulses.
(Watts=V^2 / R)
6^2 / 2 = 18 watts for half the time
0^2 / 2 = 0 watts for half the time
Mean (Average) of 9 watts.
Then using Ohm's Law, we can input the average wattage and the resistance to calculate the RMS voltage; SQRT(P x R)
SQRT(9 x 2) = SQRT(18) = 4.242vRMS
If there is one thing to remember, it is that VRMS is not a replacement for VAVG. RMS is just a way to accurately state the equivalent constant voltage. The problem with VRMS is that you cannot easily and accurately calculate the amperage. With as much stress that is placed on battery safety, it is important to know what you are asking from your batteries.
Thanks for reading, feel free to leave questions or comments below.
